.NET Framework 4 RTM became available for download alongside Visual Studio 2010 RTM the past week, with Microsoft topping the releases off with Silverlight 4 RTW. Additional resources to accompany the development platform and tools are also served by Microsoft, most of them free of charge, in order to streamline software-building efforts. It is the case of the .NET Framework 4 Migration Issues documentation published on MSDN last week. As the name implies, the resources are focused on detailing problems and breaking changes that developers can come across when adapting their projects to the latest iteration of .NET Framework.
Full read: .NET Framework 4 RTM Migration Issues on MSDN - When upgrading apps from .NET Framework 3.5 SP1 - Softpedia